XK8 exhaust without center muffler
Senior Member
Joined: Feb 2009
Posts: 262
Likes: 21
From: lakewood cal.
x pipe only no drone. pleasant exhaust note, only really effects "on throttle" sound and sound from outside vehicle. under excell it has more volume, very tasteful and not too loud. steady cruise you hardly notice the difference.
Veteran Member
Joined: Mar 2014
Posts: 2,173
Likes: 605
From: Goldsboro, NC
Thanks
Senior Member
Joined: Jun 2012
Posts: 707
Likes: 61
From: Denver, CO, USA
I am adding two glass packs after the X-pipe in a few days. I spoke with the manufacturer and he was confident that 4" diameter packs with the interior baffles facing toward the engine would cure the drone, not diminish back pressure (as desired to maintain low-end torque). 18" length, and of course 2.25" pipes. I will report back with part numbers, costs, etc after it all goes in.
Senior Member
Joined: Jul 2011
Posts: 568
Likes: 192
From: Jacksonville
"...with the interior baffles facing toward the engine would cure the drone..."
Do you mean that they suggest the glass packs should be installed "backward" from the normal flow, i.e., the flow/installation arrow should point toward the front of the car? I looked inside my glass packs and saw only essentially a straight through design with an interior wall full of holes and presumably fiberglass behind that interior wall, I saw no baffles though.
Look forward to hearing about your experience. I have an X pipe, and too had removed rear boxes and loved the sound, hated the drone, so added magnaflow glass packs which reduced drone, and reduced sound (just a bit too much sound reduction). I drilled a 1 inch hole into the exterior wall of one glass pack and brought the idle sound up nicely without adding drone, but still looking for a better option.
Do you mean that they suggest the glass packs should be installed "backward" from the normal flow, i.e., the flow/installation arrow should point toward the front of the car? I looked inside my glass packs and saw only essentially a straight through design with an interior wall full of holes and presumably fiberglass behind that interior wall, I saw no baffles though.
Look forward to hearing about your experience. I have an X pipe, and too had removed rear boxes and loved the sound, hated the drone, so added magnaflow glass packs which reduced drone, and reduced sound (just a bit too much sound reduction). I drilled a 1 inch hole into the exterior wall of one glass pack and brought the idle sound up nicely without adding drone, but still looking for a better option.
Senior Member
Joined: Jun 2012
Posts: 707
Likes: 61
From: Denver, CO, USA
The glass packs are from the manufacturer Jones and are sold online via summitracing.com. The owner told me their glass packs have directional baffles so apparently that is different from yours. They shipped Thurs but not likely to arrive in time for me to have them installed this weekend so I can really try them out on open road...
Senior Member
Joined: Aug 2009
Posts: 198
Likes: 23
From: Chino Hills, CA
Dale,
If you are in the market for an after market warranty when the SD warranty runs out, I had great success with Fidelity Platinum Level. It wasn't cheap (a little over $3k) but has covered probably close to $25K (at dealer prices) in repairs. I bought it when I suspected the transmission might go south (it did but it was 20K miles after it first started acting up.
Fidelity covered: Motor mounts, front strut, transmission (twice), door position switch, rear view mirror with headlight sensor, antenna motor, ABS speed sensors, fuel pump (twice), air mass sensor, coolant expansion tank, cd changer, differential seals (twice) and many other items I forgot. You pay for consumables: Brakes, tires, belts, hoses and fluids. They cover the rental car. Not one item was disputed with the exception of front strut where one was failing early, I had to pay for the second strut if I wanted to have them replaced as a pair.
My down side is I am at 94,000 miles and my 60,000 miles is ending this week. At this age and mileage fidelity only offers the basic engine and transmission package at around $7,500 - not worth it.
The trick is to get the new pre-warranty inspection done right before the SD warranty expires so if they find anything on the pre-warranty inspection, the SD warranty still covers it.
Lots of Luck!
If you are in the market for an after market warranty when the SD warranty runs out, I had great success with Fidelity Platinum Level. It wasn't cheap (a little over $3k) but has covered probably close to $25K (at dealer prices) in repairs. I bought it when I suspected the transmission might go south (it did but it was 20K miles after it first started acting up.
Fidelity covered: Motor mounts, front strut, transmission (twice), door position switch, rear view mirror with headlight sensor, antenna motor, ABS speed sensors, fuel pump (twice), air mass sensor, coolant expansion tank, cd changer, differential seals (twice) and many other items I forgot. You pay for consumables: Brakes, tires, belts, hoses and fluids. They cover the rental car. Not one item was disputed with the exception of front strut where one was failing early, I had to pay for the second strut if I wanted to have them replaced as a pair.
My down side is I am at 94,000 miles and my 60,000 miles is ending this week. At this age and mileage fidelity only offers the basic engine and transmission package at around $7,500 - not worth it.
The trick is to get the new pre-warranty inspection done right before the SD warranty expires so if they find anything on the pre-warranty inspection, the SD warranty still covers it.
Lots of Luck!
Senior Member
Joined: Dec 2013
Posts: 328
Likes: 86
From: Sarnia, Ontario, Canada
The glass packs are from the manufacturer Jones and are sold online via summitracing.com. The owner told me their glass packs have directional baffles so apparently that is different from yours. They shipped Thurs but not likely to arrive in time for me to have them installed this weekend so I can really try them out on open road...
Can you provide more information on which glass packs your getting. Is it one listed here? http://www.summitracing.com/int/sear...es%20glasspack
Senior Member
Joined: Jun 2012
Posts: 707
Likes: 61
From: Denver, CO, USA
glass packs after x pipe TOO QUIET
glass packs almost were installed as replacement to x pipe, they are now installed after the x pipe as planned and the car is nearly as quiet as stock
Argh, nooooo. Can't say yet if highway drone gone but clearly this has not gone the way I wanted.
Phone call to vendor coming next...
Argh, nooooo. Can't say yet if highway drone gone but clearly this has not gone the way I wanted.
Phone call to vendor coming next...
Senior Member
Joined: Dec 2013
Posts: 328
Likes: 86
From: Sarnia, Ontario, Canada
Thats a bummer to hear. I have a Magnaflow X pipe ready but can not decide on what to do next. I was thinking of purchasing the Ademash over axle sections and possibly adding some magnaflow mufflers before the rear axle. There is such a personal aspect to all this it leaves one at a loss
Senior Member
Joined: Jun 2012
Posts: 707
Likes: 61
From: Denver, CO, USA
If all the original stuff is in place, go ahead and do the center muffler replace with your new part. Jeff in AZ liked it, and House of Mufflers here in Denver just informed me that they think that is the best, affordable option too.
Enderle endorsed the rear muffler delete but the center is the best place to start it seems
House of Mufflers reviewed what I had done with others and they told me had they been in charge from day 1 they would have replaced the center muffler with an X pipe as Jeff said was good.
They also told me my glass packs will need a few hundred miles to get worn in and that my small 5 minute trips are simply not enough to generate the heat required for them to get settled and amusing. Sigh. We shall see.
Sound is fun when it works, otherwise the big risk is the time and money spent would have been better allocated to a no brainer upgrade such as the lower pulley by PowerToys. Sound can be enjoyed easily without risking a ticket though. Alas
Enderle endorsed the rear muffler delete but the center is the best place to start it seems
House of Mufflers reviewed what I had done with others and they told me had they been in charge from day 1 they would have replaced the center muffler with an X pipe as Jeff said was good.
They also told me my glass packs will need a few hundred miles to get worn in and that my small 5 minute trips are simply not enough to generate the heat required for them to get settled and amusing. Sigh. We shall see.
Sound is fun when it works, otherwise the big risk is the time and money spent would have been better allocated to a no brainer upgrade such as the lower pulley by PowerToys. Sound can be enjoyed easily without risking a ticket though. Alas
Senior Member
Joined: Jun 2012
Posts: 707
Likes: 61
From: Denver, CO, USA
for an XK8 that would be irrelevant.
However, you have variable valve timing that the same generation XKR did not get so enjoy revving the engine and hearing interesting sounds the XKR does not make in that regard
However, you have variable valve timing that the same generation XKR did not get so enjoy revving the engine and hearing interesting sounds the XKR does not make in that regard
Senior Member
Joined: Apr 2014
Posts: 233
Likes: 71
From: Stuart, FL
I have been thinking about adding this muffled X under my 2000 xk8 - It might just be perfect ( and dirt cheap to try )
http://www.summitracing.com/parts/wlk-17552
Sounds of Dynomax
http://www.summitracing.com/parts/wlk-17552
Sounds of Dynomax
Veteran Member
Joined: Mar 2014
Posts: 2,173
Likes: 605
From: Goldsboro, NC
I have been thinking about adding this muffled X under my 2000 xk8 - It might just be perfect ( and dirt cheap to try )
http://www.summitracing.com/parts/wlk-17552
Sounds of Dynomax
http://www.summitracing.com/parts/wlk-17552
Sounds of Dynomax
My guess is this would not work as it's still a muffler and is similar to what the stock center muffler is.
I'm planning, as other have said, to start with removing the center muffler and replacing with either an H or an X crossover, leaving everything else stock. This is the cheapest and best way to start and if you want more after that you can move on to removing one of the other cans on each side or remove them all and fit a single MagnaFlow or similar on each side. The choice of an H or an X crossover may be subjective. I read in one post, can't remember who, the he had an H and switched to an X and felt the H was a little deeper.
Senior Member
Joined: Feb 2014
Posts: 219
Likes: 32
From: Shreveport, LA
Good info
About 10 years ago I started working on developing a new exhaust system for my 2003.5 XKR. I started with Borla, who is north of me on the other side of L.A. My car was the mule for the project. But, they decided to not continue making systems for our cars (they already had one for the earlier models) and dropped out. I then chose to go it alone.
The first 6 to 8 prototypes were made by a local muffler shop to my designs. They were all dyno tested and some of them were tweaked a little and re-tested. The first one was an "H" pipe replacing the center dual muffler. It yielded little to no (measurable) power change, but did have an unpleasant increase in noise and tone. I would recommend against that mod.
Incidentally, the center muffler is simply two perforated pipes running side by side through a single case. Nothing special. All of the mufflers/resonators in the OEM system are straight-through perforated pipe designs. No baffles at all. There are no power gains to be realized by replacing them (with the same pipe diameter mufflers). Small differences in sound may be seen with substituting different aftermarket mufflers. Noticeable change in sound requires eliminating OEM mufflers.
Subsequent prototypes all used off-the-shelf "X" fixtures from three different manufacturers (different designs). They all improved the sound with negligible power increase. I started researching patent applications for "X" type exhausts to glean more knowledge. Quite interesting.
This led to the first MacLeod Performance Mk I X-Pipe exhaust systems. These were muffler shop built using off-the-shelf "X" fixtures and mufflers (Magnaflow, as I recall), 2.25 inch aluminized pressure-bent steel pipes in a straight back under-axle design. These consistently dyno tested with about 12 rwhp increase on forum (Road Fly) member cars. The tone and sound level received lots of positive comments.
None of the manufactured "X"s are true crossed-pipes, but instead are either stamped out "clam shell" approximations, or simply bent and siamesed pipes. (Both much cheaper to manufacture.)
This led to some flow bench testing with the different styles. The manufactured fixtures could not begin to equal the extraction effect of a true crossed-pipe "X". Probably because they had, in effect, a small plenum chamber at the point of intersection. I was also able to determine that the angle of intersection, as well as the distance from the cats, affected the power increase, sound level and tone (acoustic noise-cancelling effect of crossed-pipes). X
A lot more experimentation and testing, now dyno, flow bench and sound meter, led to a much improved MacLeod Performance Mk II X-Pipe version: laminar flow 2.5 inch mandrel bent 0.065 T304 SS tubing, true cross-pipe X, straight back under axle, custom mufflers, etc. Consistent 23-24 rwhp dyno tests increase on 4.2 XKRs. Several owners reported 10-15% improvement in mpg. Many accolades on the forums about the sound level and tone. It also stiffens the chassis quite a bit.
All this just goes to say that there is a lot more to improving our exhaust systems than just changing out a few of the parts. The entire system, from the exhaust manifold to the tips at the exit, functions as a single unit. Each part affects the sound and flow in a synergistic manner. (1+1+1+1=8 not 4)
Passing on the following lessons learned may help you in experimenting with your own system.
1. The OEM system is a little restrictive (power reducing) on the XK8s. It is grossly restrictive (same system handling 33% more flow) on the XKRs.
2. The most power robbing part of the OEM (and several after-market) exhaust systems is the over-the-axle pipes. On the OEM system they are crimped down to between 0.75 and 1 inch in two places on each pipe. There'll be little to no performance improvement until these are replaced. They also affect the sound (negatively, in my opinion).
3. Pipe diameter: 2.25 minimum, mandrel bent; 2.50 inch noticeably better, mandrel bent. (Muffler/Exhaust shops use pressure benders which crimp the pipe diameter down in the bends. Mandrel bending maintains a constant diameter through the bends. Pressure bends not only restrict, but also disrupt the laminar flow, as do the welds.)
4. The sound and performance (a little) can be improved with a muffler shop built system. It will be cheaper than a complete cat-back after-market T304 SS exhaust system, but you'll be getting a lot less, also.
I would suggest, if you are going that way, to not waste your time and money cutting and patching pieces of the OEM system. At least replace everything between the cats and rear mufflers with an "X" fixture and under axle pipes--eliminating the center resonators as well. If possible, replace the rear mufflers also and increase the entire system diameter to 2.25 inches. The system will still be a mix of steel and possibly low grade 409 SS parts, but it will sound better.
Bending the pipes correctly to fit up next to the rear cross member without touching it (which will produce a drone inside the car) and not decreasing the ground clearance is a bit tricky.
Be sure to get a price for doing all this before you start. It can add up quickly.
If you do this and still want to change the sound level afterwards, let me know. There are some other tricks to change the sound level and tone.
Hope this helps.
The first 6 to 8 prototypes were made by a local muffler shop to my designs. They were all dyno tested and some of them were tweaked a little and re-tested. The first one was an "H" pipe replacing the center dual muffler. It yielded little to no (measurable) power change, but did have an unpleasant increase in noise and tone. I would recommend against that mod.
Incidentally, the center muffler is simply two perforated pipes running side by side through a single case. Nothing special. All of the mufflers/resonators in the OEM system are straight-through perforated pipe designs. No baffles at all. There are no power gains to be realized by replacing them (with the same pipe diameter mufflers). Small differences in sound may be seen with substituting different aftermarket mufflers. Noticeable change in sound requires eliminating OEM mufflers.
Subsequent prototypes all used off-the-shelf "X" fixtures from three different manufacturers (different designs). They all improved the sound with negligible power increase. I started researching patent applications for "X" type exhausts to glean more knowledge. Quite interesting.
This led to the first MacLeod Performance Mk I X-Pipe exhaust systems. These were muffler shop built using off-the-shelf "X" fixtures and mufflers (Magnaflow, as I recall), 2.25 inch aluminized pressure-bent steel pipes in a straight back under-axle design. These consistently dyno tested with about 12 rwhp increase on forum (Road Fly) member cars. The tone and sound level received lots of positive comments.
None of the manufactured "X"s are true crossed-pipes, but instead are either stamped out "clam shell" approximations, or simply bent and siamesed pipes. (Both much cheaper to manufacture.)
This led to some flow bench testing with the different styles. The manufactured fixtures could not begin to equal the extraction effect of a true crossed-pipe "X". Probably because they had, in effect, a small plenum chamber at the point of intersection. I was also able to determine that the angle of intersection, as well as the distance from the cats, affected the power increase, sound level and tone (acoustic noise-cancelling effect of crossed-pipes). X
A lot more experimentation and testing, now dyno, flow bench and sound meter, led to a much improved MacLeod Performance Mk II X-Pipe version: laminar flow 2.5 inch mandrel bent 0.065 T304 SS tubing, true cross-pipe X, straight back under axle, custom mufflers, etc. Consistent 23-24 rwhp dyno tests increase on 4.2 XKRs. Several owners reported 10-15% improvement in mpg. Many accolades on the forums about the sound level and tone. It also stiffens the chassis quite a bit.
All this just goes to say that there is a lot more to improving our exhaust systems than just changing out a few of the parts. The entire system, from the exhaust manifold to the tips at the exit, functions as a single unit. Each part affects the sound and flow in a synergistic manner. (1+1+1+1=8 not 4)
Passing on the following lessons learned may help you in experimenting with your own system.
1. The OEM system is a little restrictive (power reducing) on the XK8s. It is grossly restrictive (same system handling 33% more flow) on the XKRs.
2. The most power robbing part of the OEM (and several after-market) exhaust systems is the over-the-axle pipes. On the OEM system they are crimped down to between 0.75 and 1 inch in two places on each pipe. There'll be little to no performance improvement until these are replaced. They also affect the sound (negatively, in my opinion).
3. Pipe diameter: 2.25 minimum, mandrel bent; 2.50 inch noticeably better, mandrel bent. (Muffler/Exhaust shops use pressure benders which crimp the pipe diameter down in the bends. Mandrel bending maintains a constant diameter through the bends. Pressure bends not only restrict, but also disrupt the laminar flow, as do the welds.)
4. The sound and performance (a little) can be improved with a muffler shop built system. It will be cheaper than a complete cat-back after-market T304 SS exhaust system, but you'll be getting a lot less, also.
I would suggest, if you are going that way, to not waste your time and money cutting and patching pieces of the OEM system. At least replace everything between the cats and rear mufflers with an "X" fixture and under axle pipes--eliminating the center resonators as well. If possible, replace the rear mufflers also and increase the entire system diameter to 2.25 inches. The system will still be a mix of steel and possibly low grade 409 SS parts, but it will sound better.
Bending the pipes correctly to fit up next to the rear cross member without touching it (which will produce a drone inside the car) and not decreasing the ground clearance is a bit tricky.
Be sure to get a price for doing all this before you start. It can add up quickly.
If you do this and still want to change the sound level afterwards, let me know. There are some other tricks to change the sound level and tone.
Hope this helps.
Dynamax x-flow on XKR
I have been thinking about adding this muffled X under my 2000 xk8 - It might just be perfect ( and dirt cheap to try )
http://www.summitracing.com/parts/wlk-17552
Sounds of Dynomax
http://www.summitracing.com/parts/wlk-17552
Sounds of Dynomax
. I hate being ricer-bait!
Junior Member
Joined: Sep 2017
Posts: 23
Likes: 2
From: Keller, Texas
Hey man,
Tom Vroom Keller Texas here, and yes that is my real last name. had some questions about your exhaust mods on your XK8. My 99 model is stock and some talk of just removing the 4 aft silencers and a lot talk about removing the center muffler and going with an X pipe. I believe that's what you did? Did you retain all 4 silencers?
You are pretty near me so if we could meet up I'll buy lunch if I can hear your's before I decide what to do?
TV
Tom Vroom Keller Texas here, and yes that is my real last name. had some questions about your exhaust mods on your XK8. My 99 model is stock and some talk of just removing the 4 aft silencers and a lot talk about removing the center muffler and going with an X pipe. I believe that's what you did? Did you retain all 4 silencers?
You are pretty near me so if we could meet up I'll buy lunch if I can hear your's before I decide what to do?
TV
Veteran Member
Joined: Jan 2017
Posts: 1,042
Likes: 429
From: Nevada, USA
the aft four boxes are straight through, thus not mufflers but resonators. the internal design of the center box is not known to me. if this is also a straight through, then there should be no change in the power band unless pipe diameter is changed. the limiting factor is the catalyst setup in both power band and sound to a large degree. an x-pipe tends to improve the exhaust scavenging issues of a V8 and eliminates the burble of a true dual exhaust. interestingly, if there is adequate capacity (pipe diameter and flow capacity of the system) a V8 would get better performance from a single exhaust as the forward Y acts like an x-pipe. the issue is that the system would have to be very large with commensurate packaging issues and people expect dual exhausts on performance V8 engines.
when these cars were raced the removal of said catalyst made the largest difference in the power band.
when these cars were raced the removal of said catalyst made the largest difference in the power band.